Abstract If there were a simple and accurate means to ?take the pulse? of a tooth, (i.e. functionally similar to a pulse oximeter that could be clipped on a tooth rather than the tip of a finger) the quality and cost of dental care would be significantly improved. The ability to measure dental pulp blood flow provides the most direct means to determine the viability of a tooth and is a vital piece of information required for nearly all dental management decisions. It is an unmet need identified in NIDCD?s PA-15-336. Conventional blood flow detection approaches are precluded by the rigid structure of teeth and the invariant volume of vascular space within the root of the tooth. To circumvent the latter constraint we combined principles from two separate modern optical technologies (laser Doppler and coherence gated tomography) to create a hybrid technology with unique capabilities, ?coherence gated Doppler? (CGD) (US Patent 9,486,140). But the challenge for dentists is not just the certainty of information on whether a tooth is viable or not, but in the prompt access to that information. The dentist can wait until the signs of death becomes clear before making a therapeutic decision. But the delayed action can have significant negative consequences for preserving function. Examples include bone resorption caused by chronic infection requiring expensive and time-consuming bone grafts if the tooth is to be replaced by an implant, greater instability if that tooth is to be left in place after receiving endodontic therapy, and unnecessary pain, cost, and time for repeat office visits by the patient. Current standard of practice has evolved to a suboptimal compromise between diagnostic certainty and promptness of intervention. If high diagnostic accuracy can be provided painlessly, at low cost within minutes by the dental assistant, it will have a profound impact on dentistry. The broad goal of this STTR application is to demonstrate the feasibility of ?transmission mode? CGD as such a technology. Specifically, this phase I project will determine whether CGD has the sensitivity and specificity to detect blood flow within the root of a tooth while rejecting any flow signal from outside the tooth. This proof of concept demonstration will be carried out in freshly extracted teeth and in a ferret canine teeth animal model. Furthermore, the performance of CGD will be compared against the predicate laser Doppler flowmetry technology.